OAK Hose - Too Big

[Rob From Wisconsin]

I'm looking into putting an OAK on our existing stove.
The only thing that is getting in the way is the ugly, over-sized
hose that will make my nice stove look like a "Borg" from Star Trek.

From what I've measured, the size they recommend is way overkill -
probably at least twice the width of the std. air opening of the stove.

I'm tempted to run a reduced diameter tube/hose to the "proximity"
of the air input, and leaving it at that......

 

[fossil]

Seems all that would accomplish is having a hole in your house. Why bother? Rick

 

[blades]

in my old place I had a 4" worked fine.

 

[Highbeam]

What size do they recommend? Typical is 3-4 inches which isn't big at all. Since your stove is a natural draft appliance it would be very easy to introduce a restrictive intake tube and ruin the stove's performance.

I agree that unless you can get a sealed connection to the stove then you are not properly utilizing the OAK.

 

[DAKSY]

The Tribute Manual specifies a 3" min dia OAK tube...

 

[blades]

You could look at it this way, 6" flue (output) = 6" intake, this would guarantee a non-negative atmospheric pressure inside, at least until a bath or kitchen exhaust fan is turned on or the clothes dryer. Make up air has to come from somewhere, generally every chink to the outside in your dwelling.

 

[fossil]

You could look at it this way, 6" flue (output) = 6" intake...

Not exactly. The air entering for combustion is relatively cool, and therefore more dense, requiring a smaller cross-sectional area for the required mass flow rate than the much hotter exiting flue gases, which are much less dense. I imagine any stove with a 6" flue collar should run just fine with a 3" OAK hose, provided there aren't any other significant factors in play. An OAK, actually, properly hooked up, should make the woodburning appliance pretty much oblivious to whatever's going on in the house to mildly affect pressure differential from inside to outside, unlike an appliance which is taking all of its combustion air directly from the living space. Rick

 

[semipro]

You could look at it this way, 6" flue (output) = 6" intake...

Not exactly. The air entering for combustion is relatively cool, and therefore more dense, requiring a smaller cross-sectional area for the required mass flow rate than the much hotter exiting flue gases, which are much less dense. I imagine any stove with a 6" flue collar should run just fine with a 3" OAK hose, provided there aren't any other significant factors in play. An OAK, actually, properly hooked up, should make the woodburning appliance pretty much oblivious to whatever's going on in the house to mildly affect pressure differential from inside to outside, unlike an appliance which is taking all of its combustion air directly from the living space. Rick

Fossil is on the right track here. It has to do with mass flow and can be calculated using the "Ideal Gas Law". I did the math one day for my stove and came up with somewhere between a 3" and 4" dia. inlet size. As someone else mentioned there is also some frictional losses in the inlet hose/pipe so going with the 4" for a 6" outlet is about right. Curiously, that's the size recommended for all the stoves I've used and seen...lately.